Laminates of Polysilazane And Carbon Fiber Reinforced Polymer

ABSTRACT

Disclosed are laminates comprising a carbon fiber reinforced polymer sheet and a layer of polysilazane and methods for producing such laminates.

FIELD

This disclosure relates to laminates comprising a sheet of carbon fiberreinforced polymer and a polysilazane layer.

BACKGROUND

Fiber reinforced polymers (FRPs) are widely used to create structuralelements and parts used in aerospace, automotive, watercraft, sportinggoods, and civil/structural engineering applications among others. FRPsare strong, light-weight materials with high strength-to-weight ratios.FRPs typically are formed by combining fibers and an uncured bindingpolymer and then curing the binding polymer. A particular type of FRP iscarbon fiber reinforced polymer (CFRP). CFRPs are increasingly commonand have many different applications.

CFRPs are used in various devices in combination with metal components.For example, aircraft engine thrust reverser inner walls often employ acellular core, typically in a honeycomb configuration, and a skin ofCFRP connected to the core. The CFRP skin of a thrust reverser wall isnormally perforated to reduce noise produced by air flowing through thecavity adjacent the thrust reverser wall.

CFRPs are also used in combination cellular cores to make equipment forvarious sports. Examples of such equipment include bicycle disc wheels,skis, and snowboards.

Unless the CFRP and metal components are completely isolatedelectrically from each other, the combination of CFRP and a metalcomponent under appropriate conditions (conditions permitting galvaniccoupling) will result in a flow of electrons from the metal to the CFRP,i.e., galvanic corrosion or, in other words, oxidation of the metal.

As a result, there is a need to protect devices in which metalcomponents, e.g., aluminum honeycomb core material used in aircraftengine thrust reversers, are electrically connected or galvanicallycoupled to CFRP from oxidation caused by moisture.

SUMMARY

This disclosure provides a solution to the problem of galvanic corrosionof metal components in devices in which the metal component is inelectrical or galvanic communication with CFRP. This solution involvesusing a polysilazane or mixture thereof as a barrier material betweenCFRP and/or a metal component and oxygen or moisture in the environmentsurrounding the device.

Thus, this disclosure involves applying a coating of a polysilazane ontothe CFRP to prevent water and oxygen from contacting the carbon fiberswithin CFRP. As a result, an oxidation/reduction reaction is preventedor inhibited by blocking or substantially diminishing the reduction ofoxygen in or at the surface of a CFRP, i.e., the CFRP does not act as acathode, and the metal component does not act as an anode. The metalcomponent therefore does not function as an anode and does not loseelectrons; in short, it is not oxidized and does not become corroded.

Alternatively, a polysilazane or mixture thereof is applied to the metalcomponent to prevent galvanic communication with the CFRP by inhibitingwater and electrolyte from creating an electrical or galvanic connectionbetween the metal component and CFRP.

In one aspect, this disclosure provides a laminate comprising a sheet ofcarbon fiber reinforced polymer (CFRP) coated with a layer ofpolysilazane.

In another aspect, this disclosure provides a laminate comprising asheet of carbon fiber reinforced polymer (CFRP), the sheet having afirst side and a second side opposite the first side; and a layer ofpolysilazane covers the first side of the sheet of CFRP.

In another aspect, this disclosure provides a device comprising a metalcellular core adjacent a sheet of carbon fiber reinforced polymer(CFRP), the sheet having a first side and a second side opposite thefirst side; wherein the metal cellular core is coated with a layer ofpolysilazane.

In another aspect, this disclosure provides a method for inhibitingoxidation of a metal structure electrically connected to a sheet ofcarbon fiber reinforced polymer (CFRP), the method comprising applying aliquid polysilazane composition to the sheet of CFRP and allowing thecomposition to cure.

In an aspect, this disclosure provides a method for inhibiting oxidationof a metal structure which is adjacent to a sheet of carbon fiberreinforced polymer (CFRP), the method comprising applying a liquidpolysilazane composition to the metal structure and allowing thecomposition to cure.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a side cutaway view of a laminate of this disclosure.

FIG. 2 is a side cutaway view of a laminate of this disclosure.

FIGS. 3a, 3b, and 3c are side cutaway views of a laminate adjacent ametal structure.

FIG. 4 is a perspective view of a laminate with perforations.

FIG. 4a is a side cutaway view taken along line A-A of FIG. 4 through aperforation in a laminate of this disclosure.

FIG. 5 is a perspective view of a laminate with perforations adjacent ametal structure.

FIG. 6 is a cross section of a commercial aircraft jet power plant.

FIG. 7 is an isometric cut away view of a thrust reverser inner wall.

FIG. 8 is a flow chart illustrating an exemplary method for inhibitingoxidation of a metal structure electrically connected to a sheet ofcarbon fiber reinforced polymer (CFRP)

FIG. 9 is a flowchart illustrating an exemplary method for inhibitingoxidation of a metal structure which is adjacent to a sheet of carbonfiber reinforced polymer (CFRP).

DETAILED DESCRIPTION

“Polysilazane” as used herein means oligomers, cyclic, polycyclic,linear polymers, or resinous polymers having multiple Si—N repeatingunits in the compound.

“Electrical communication” and “galvanic communication” are usedinterchangeably herein and refer to sufficient connection betweenmaterials to permit the transfer or movement of electrons between thematerials.

This disclosure addresses galvanic corrosion of metal components indevices in which the metal component is in electrical or galvaniccommunication with CFRP. The terms metal and metal alloy are usedinterchangeably herein. This disclosure involves using a polysilazane ormixture thereof as a barrier material between CFRP and/or a metalcomponent and oxygen or moisture in the environment surrounding thedevice.

Devices with metal components connected to CFRP are seldom manufacturedin a way that completely isolates these parts from each other. The metalcomponents in these devices are therefore susceptible to oxidation andcorrosion. For example, the perforations in some CFRP sheets, such as,for example, thrust reverser wall skins, have exposed carbon fiberswhich allows oxygen to contact the carbon fibers within the skin. Thus,when the cellular core of, e.g., a thrust reverser wall is fashionedfrom a metal, e.g., aluminum or aluminum alloy, and in contact withCFRP, the aluminum is susceptible to oxidation and corrosion.

Further, oxidation and corrosion are increased in damp or wetenvironments due to water and electrolyte bridging between CFRP and themetal components. The galvanic corrosion process increases the corrosionrate of aluminum over the rate that would normally occur when thealuminum is not galvanically coupled to the CFRP by a factor of 100 ormore.

Thus, this disclosure involves applying a coating of a polysilazane ormixture of polysilazanes, typically as a solution or suspension ofpolysilazane in a solvent, onto the CFRP and allowing the coating tocure, which results in a laminate having a layer of polysilazane on theCFRP that is water-proof and has excellent water-sheddingcharacteristics. The polysilazane layer prevents water and oxygen fromcontacting the exposed carbon fibers within CFRP. This, in turn,prevents an oxidation/reduction reaction between the CFRP and the metalcomponent by blocking or substantially diminishing the reduction ofoxygen in or at the surface of a CFRP, i.e., the CFRP does not act as acathode, and the metal component does not act as an anode. The metalcomponent therefore does not lose electrons; in short, the metalcomponent is not oxidized and does not become corroded.

As an alternative or in addition to coating the CFRP, a polysilazane ormixture thereof is applied to the metal component to prevent galvaniccommunication with the CFRP by inhibiting water and electrolyte fromcreating an electrical or galvanic connection between the metalcomponent and CFRP.

This disclosure provides laminates comprising a sheet of carbon fiberreinforced polymer (CFRP) coated with one or more polysilazanes. Thepolysilazane coating may be a single layer of a plurality of layers. Thepolysilazanes are typically applied as a liquid polysilazanecomposition. These compositions are a formulation of the polysilazane ora mixture of polysilazanes in a carrier liquid, i.e., a solution orsuspension of the polysilazane(s) in a solvent system.

As shown in FIG. 1 and FIG. 2, this disclosure provides a laminate 100comprising a sheet of carbon fiber reinforced polymer (CFRP) 102 andpolysilazane coating. CFRP sheet 102 has a first side 110 and a secondside 120 opposite the first side. The coating covers at least a portionof one side of sheet 102.

The polysilzane composition can be applied to one or both sides of thesheet so that, after cure, there is a polysilazane coating on one sideor on both sides of sheet 102. Thus, as shown in FIG. 1, laminate 100can comprise a CFRP sheet 102, the sheet having a first side 110 and asecond side 120 opposite the first side; and a layer of polysilazane 130covering at least a portion of first side 110 of the sheet 102. Thisprevents water accumulation and an oxidation/reduction reaction.Additional corrosion protection can be obtained by applying polysilazaneto both sides of sheet 102. This alternative is shown in FIG. 2, whereCFRP sheet 102 has first side 110 and second side 120 opposite the firstside 110; and layer of polysilazane 130 covering first side 110 andlayer of polysilazane 140 covering the second side 120 of sheet 102. Ineither configuration, polysilazane can cover a portion of a side of CFRPsheet 102 or, preferably, the entire side of CFRP sheet 102. Maximumcorrosion resistance is achieved by coating an entire side of CFRP sheet102.

The laminates of this disclosure can be employed in devices in which oneor more CFRP sheets are adjacent a metal or metal alloy structure. Theresulting devices have improved corrosion resistance compared to suchdevices that lack the polysilazane coating.

FIGS. 3a-3c depict a single laminate 100 adjacent a metal structure 160.This disclosure also encompasses devices in which to two or morelaminates 100 are adjacent metal structure 160, e.g., on opposite sidesof metal structure 160. In addition, this disclosure encompasses devicesin which a single laminate 100 is adjacent two or more metal structures160, e.g., a first metal structure adjacent first side 110 and a secondmetal structure adjacent second side 120.

FIGS. 3a-3c depict a single laminate 100 having different configurationsof polysilazane on sheet 102. In FIG. 3a , laminate 100 has polysilazanelayer 130 on first side 110 and metal structure 160 is adjacent secondside 120. In FIG. 3b , laminate 100 has polysilazane layer 140 on secondside 120 and metal structure 160 is adjacent second side 120. In FIG. 3c, laminate 100 has polysilazane layers 130 and 140 on first side 110second side 120, respectively, and metal structure 160 is adjacentsecond side 120.

In any of the above configurations, laminate 100 may be in electricalcontact with metal structure 160 or electrically insulated from metalstructure 160. In many devices electrical insulation is difficult toachieve and, as noted above, at least some minimal electrical connectionexists which can lead to oxidation and corrosion of the metal. Thepolysilazane layer or coating is water-proof and has excellentwater-shedding characteristics Laminate 100 therefore can minimizecorrosion of metal structure 160 by preventing water from contactingmetal structure 160 and CFRP sheet 102 simultaneously and/or bypreventing oxygen from reaching carbon fibers within sheet 102, which inturn prevents or minimizes an oxidation-reduction reaction in which theCFRP sheet 102 would function a cathode and metal structure 160 wouldfunction as the anode.

Although FIGS. 3a-c show metal structure 160 adjacent second side 120,it can be adjacent first side 110 and/or second side 120 of laminate100.

Certain uses of laminate 100 require that sheet 102 have one or moreholes or perforations extending at least partially through sheet 102. Anexample of a laminate having a plurality of perforations 170 is shown inFIG. 4. As explained more fully below, such laminates are useful formaking parts of aircraft engines.

Perforations 170 are shaped and sized according to the ultimate use ofthe device. They can be multi-sided, irregularly shaped, orsubstantially circular. For example, perforations 170 can have adiameter of from about 0.75 (0.03 in) to about 1.5 mm (0.06 in), or fromabout 1 mm (0.04 in) to about 1.25 mm (0.05 in).

As shown in FIG. 4a , perforations 170 include perforation sidewalls172. Laminate 100 can be manufactured in a manner that results in apolysilazane sidewall coating 174 on the sidewalls 172 of perforations170. Polysilazane sidewall coating 174 on sidewalls 172 providesadditional water-proofing and water-shedding to the CFRP to furtherreduce corrosion of a metal structure in contact with the CFRP.

Polysilazane sidewall coating 174 can have a thickness of from about1-10 μm, from about 1-5 μm, or from about 2-3 μm. Such thicknesses aresufficient to achieve the corrosion-reducing properties of the laminateand only minimally change the diameter of the perforations.

Metal structure 160 can be a metal cellular core, preferably a honeycombcore, such as an aluminum honeycomb core. Honeycomb cores are used in avariety of applications including aircraft and sporting goods, e.g.,bicycle disc wheels, skis and snowboards. In certain examples, the metalcellular core is a metal honeycomb core in an aircraft engine thrustreverser. The metal honeycomb core can be aluminum or an aluminum alloy.

FIG. 5 depicts a device in which metal structure 160 is a honeycomb core162 and the honeycomb core is adjacent laminate 100. In certain devices,laminate 100 and honeycomb core 162 are physically connected to oneanother. In some devices, laminate 100 and honeycomb core 162 arephysically connected but electrically insulated from each other.Alternatively, laminate 100 can be in electrical contact with honeycombcore 162. As mentioned above, when laminate 100 is in electrical contactwith a metal structure such as honeycomb core 162, the polysilazanelayer of the laminate provides enhanced corrosion protection to themetal structure.

Sheet 102 of laminate 100 is depicted in FIG. 5 as being perforated;alternatively sheet 102 lacks perforations.

The laminates of this disclosure are particularly useful formanufacturing components of aircraft engine thrust reversers. A thrustreverser wall is a sandwich structure with a top layer, typically ofepoxy impregnated perforated carbon fiber fabric, a honeycomb core, anda bottom layer of material that can be epoxy impregnated carbon fiberfabric.

A coating or layer of polysilazane on the CFRP repels water and preventsreduction of oxygen. Where the CFRP sheet and metal structure arecomponents of a thrust reverser wall, and the CFRP sheet is perforated,the combination of the polysilazane coating and the perforations permitsthe metal to rapidly dry as air flows through the thrust reverser. Thisprevents water accumulation on the thrust reverser walls and within thereverser core; as a consequence, there will be less corrosion of thecore.

As seen in FIG. 6, a typical commercial aircraft jet power plant 201comprises the engine 202, associated cowling 203, fan 204, and thrustreverser cowling 205. The fan 204 draws air through the power plant 201as indicated by the fan air flow arrows 207. The fan air flow enterscowling 203 and passes through the annular fan air bypass duct 208between the thrust reverser inner wall 210 and the thrust reverser outerwall 212. Thrust reverser inner wall 210 has an inside surface 214 andan outer surface 216.

As seen in FIG. 7, thrust reverser inner wall 210 is a sandwichstructure with a top layer 320 of perforated carbon fiber, typically acarbon fiber reinforced epoxy. Perforations 322 are manufactured intothe top layer 320 in any conventional manner, e.g., when the layer ispartially cured on a perforation layup tool (not shown). Theperforations 322 are designed to maintain proper acoustic properties ofthe thrust reverser inner wall 210. When installed in the power plant201, the top face 324 of perforated carbon fiber top layer 320 directlyinterfaces with the fan air flow 207.

Perforations 322 are substantially circular and are sized to reducenoise produced by air flowing through the cavity adjacent the thrustreverser wall. Preferred perforations 322 have a diameter of from about0.75 (0.03 in) to about 1.5 mm (0.06 in). More preferably, theperforations have a diameter of from about 1 mm (0.04 in) to about 1.25mm (0.05 in).

Optimum noise reduction is obtained with perforations covering fromabout 1-20%, from about 5-18%, or from about 7-14% of the area of wall210.

A layer of adhesive 236 is typically used to adhere the perforatedcarbon fiber top layer 320 to a metal, e.g., aluminum or aluminum alloy,honeycomb core 330. The adhesive can be reticulated to maintain theperforated holes after bonding for acoustic characteristics and affordmaximum adhesion between the sheet and the metal component. Suitableadhesives include polyimide and bismaleimide adhesive materials.

In certain examples, honeycomb core 330 includes aluminum or aluminumalloy reinforced sheets 332, corrugated to form specific honeycomb cells335, then bonded with an adhesive resin 333 and coated with the same ora different resin (not shown).

Top layer 320 is coated with a polysilazane to produce a waterproof andwater-shedding layer 334 on thrust reverser inner wall 210. Wall 210 is,therefore, a laminate comprising a sheet of CFRP and layer ofpolysilazane. Polysilazane layer 334 has a thickness of from about 1-10μm, from about 1-5 μm, or from about 2-3 μm. This thickness minimallychanges the diameter of the perforations so that the sound-reducingcharacteristics of the perforations are maintained.

The polysilazane layer is very water-repellant and allows CFRP laminatewall 210 to rapidly shed water. Rapid shedding of water permits core 330to rapidly dry out as air flows through the structure. This preventswater accumulation on the thrust reverser walls and within the reversercore; as a consequence, there will be less corrosion of the core.

Because it reduces water-mediated corrosion of the core, layer 334eliminates or reduces the need for an electrically insulating layerbetween top layer 320 and honeycomb core 330. However, in certainexamples, an optional layer of electrically insulating material (notshown) may be located between the CFRP sheet and the honeycomb core toelectrically insulate the core from the CFRP layer. A suitableelectrically insulating material is a layer of fiberglass.

Thrust reverser outer wall 212 can also be manufactured to include alaminate as described for inner wall 210.

A base layer 338 is adhered to the bottom surface 340 of honeycomb core330, for example by a layer of adhesive 342. The base layer may be aCFRP or a metal such as aluminum or aluminum alloy.

In certain examples, the thrust reverser inner wall 210 has aninsulation layer 345 adhered to the bottom of base layer 338, whereinthe insulation layer is the layer adjacent and closest to the engine 202when installed in the power plant.

Manufacturing the laminates of this disclosure comprises applying aliquid polysilazane composition to a sheet of CFRP and allowing thecomposition to cure. Curing of the polysilazane is conveniently carriedout at ambient temperature and pressure; curing can also be acceleratedwith heat.

Suitable solvents for use in the liquid polysilazane composition areinert to the polysilazane, i.e., they function as a carrier for thepolysilazane and do not react with the polysilazane. Such solventsinclude hydrocarbons, C₁-C₆ alkyl esters of C₂-C₆ carboxylic acids, andmixtures thereof. Representative hydrocarbons include straight orbranched chain C₇-C₁₀ hydrocarbons (e.g., pentane, hexane, and heptane),cyclic C₅-C₁₀ saturated hydrocarbons such as cyclopentane, cyclohexane,cycloheptane, etc., and aromatic hydrocarbons such as toluene andxylene. Representative alkyl esters include t-butyl acetate. The liquidpolysilazane composition can also contain silanes such as3-aminopropyltriethoxysilane.

In certain examples, the polysilazane is present in the liquidpolysilazane composition at a concentration of about 10-50% by weight ofthe composition. In other examples, the polysilazane is present in theliquid polysilazane composition at a concentration of about 10-20% byweight of the composition. In other examples, the polysilazane ispresent in the liquid polysilazane composition at a concentration ofabout 12-15%, or 13-14%, by weight of the composition.

Suitable liquid polysilazane compositions include Durazane® (e.g.,Durazane® 1500 RC and 1500 SC, AGS TutoProm®, and a polysilazaneresin/solvent blend commercially available from Huntington SpecialtyChemicals as HS-922.

Polysilazanes are polymers in which silicon and nitrogen atoms alternateto form the basic backbone. Each silicon atom is bound to two separatenitrogen atoms and each nitrogen atom is bound to two (2) silicon atoms;consequently both chains and rings of the formula [R₁R₂Si—NR₃]_(n)occur. R₁-R₃ independently represent hydrogen atoms or organicsubstituents. Typical organic substituents are alkyl groups having from1-6 carbon atoms and unsaturated groups such as allyl and vinyl.

When all the R groups are hydrogen atoms, the polymer is designated as aperhydropolysilazane; perhydropolysilazanes are also known as inorganicpolysilazanes and can be represented by the formula [H₂Si—NH]_(n).

When hydrocarbon substituents are bound to the silicon atoms, thepolymers are designated as organopolysilazanes. Organopolysilazanes arealso known as organic polysilazanes and can be represented by theformula [R₁R₂Si—NH]_(n), where R₁ and R₂ are independently hydrogen orhydrocarbon groups wherein at least one of R₁ and R₂ is not hydrogen.Preferred R₁ and R₂ groups are alkyl groups having from 1-6 carbonatoms, vinyl, and allyl.

Suitable polysilazanes for use herein are disclosed in U.S. Pat. Nos.4,395,460 and 6,329,487.

The polysilsazanes disclosed in U.S. Pat. No. 4,395,460 can be preparedby contacting and reacting in an inert, essentially anhydrous,atmosphere at a temperature in the range of 25° C. to 370° C.:

-   -   (A) ammonia and    -   (B) chlorine-containing disilanes selected from the group        consisting of        -   (i) a chlorine-containing disilane having the general            formula [Cl_(a)R_(b)Si]₂ and        -   (ii) a mixture of chlorine-containing disilanes having the            general formula

[Cl_(c)R_(d)Si]₂

-   -   -   wherein            -   a has a value of 1.5-2.0;            -   b has a value of 1.0-1.5;            -   the ratio of c to d is in the range of 1:1 to 2:1;            -   the sum of a+b is equal to three;            -   the sum of c+d is equal to three; and            -   R in each case is selected from a group consisting of                the vinyl group, an alkyl radical of 1-3 carbon atoms                and the phenyl group.

The polysilsazanes disclosed in U.S. Pat. No. 6,329,487 can be preparedby

a) introducing at least one halosilane having at least one Si—H bondinto liquid anhydrous ammonia, the amount of liquid anhydrous ammoniabeing at least twice the stoichiometric amount of silicon-halide bondson the halosilane, the halosilane reacting with the anhydrous liquidammonia to form a precursor ammonolysis product and an ammonium halidesalt or acid thereof, the ammonium halide salt or acid thereof beingsolubilized and ionized in the anhydrous liquid ammonia therebyproviding an acidic environment; and

b) maintaining the precursor ammonolysis product in the acidicenvironment for a sufficient time to reduce the number of Si—H bondsrelative to the quantity of Si—H bonds that are incorporated into thenovel silazane and/or polysilazane from the halosilane of step (a).

The polysilazane used to form a polysilazane layer on the CFRP sheet canbe an inorganic polysilazane, an organic polysilazane, or a mixturethereof. In some examples, the polysilazane is an inorganicpolysilazane, or a mixture thereof.

In other examples, the polysilazane is an organic polysilazane, or amixture thereof.

During manufacture of a laminate as disclosed herein, the liquidpolysilazane composition can be applied to the CFRP sheet at a thicknessthat produces, upon cure of the polysilazane, a layer of polysilazanehaving any desired thickness. Preferred thicknesses for the polysilazanelayer are about 1-10 μm, about 1-5 μm, or about 2-3 μm. Such thicknessesare sufficient to create an adequate water and oxygen barrier withoutclogging or otherwise changing the diameter any perforations present inthe CFRP sheet. Suitable application rates to afford such layerthicknesses are from about 5-15 mL/m².

While a particular implementation has been described, it will beapparent to persons skilled in the art to which this disclosure pertainsthat many modifications and variations thereto are possible withoutdeparting from the spirit and scope.

Accordingly, the scope of this disclosure should be considered limitedonly by the spirit and scope of the elements of the appended claims ortheir reasonable equivalents.

Clause 1. A laminate comprising a sheet of carbon fiber reinforcedpolymer (CFRP), the sheet having a first side and a second side oppositethe first side; and a layer of polysilazane covering one or both of thefirst side and the second side of the sheet of CFRP.

Clause 2. A laminate according to clause 1, wherein the first side ofthe sheet of CFRP contains perforations.

Clause 3. A laminate according to clause 1 or clause 2, wherein at leastone of the first side and the second side of the sheet of CFRP is inelectrical communication with a metal.

Clause 4. A laminate according to clause 2, wherein at least one of thefirst side and the second side of the sheet is in electricalcommunication with a metal cellular core or a metal alloy cellular core.

Clause 5. A laminate according to any one of clauses 2-4, wherein theperforations have a diameter of from about 0.75 (0.03 in) to about 1.5mm (0.06 in).

Clause 6. A laminate according to any one of clauses 2-5, wherein thesidewalls of the perforations are coated with polysilazane.

Clause 7. A laminate according to any one of clauses 1-6, wherein thelayer of polysilazane has a thickness of from about 1-10 μm.

Clause 8. A laminate according to any one of clauses 2-7, wherein theperforations cover from about 5-20% of the first side of the sheet.

Clause 9. A laminate according to any one of clauses 1-8, wherein thepolysilazane is an inorganic polysilazane, an organic polysilazane, or amixture thereof.

Clause 10. A laminate according to any one of clauses 1-9, wherein thesheet of CFRP comprises exposed carbon fibers.

Clause 11. A laminate according to any one of clauses 1-10, wherein themetal cellular core comprises aluminum.

Clause 12. A aircraft engine thrust reverser comprising a laminateaccording to any one of clauses 1-11.

Clause 13. A method for inhibiting oxidation of a metal structureelectrically connected to a sheet of carbon fiber reinforced polymer(CFRP), wherein the sheet of CFRP has a first side and a second side andthe second side is in electrical communication with the metal structure,the method comprising applying a liquid polysilazane composition to atleast the first side of the sheet of CFRP and allowing the compositionto cure.

Clause 14. A method according to clause 13, wherein the liquidpolysilazane composition comprises an inorganic polysilazane, an organicpolysilazane, or a mixture thereof.

Clause 15. A method according to clause 13 or clause 14, wherein theliquid polysilazane composition comprises a solution of a polysilazaneand a solvent inert to the polysilazane.

Clause 16. A method according to clause 15, wherein the solvent isselected from hydrocarbons, C₁-C₆ alkyl esters of C₂-C₆ carboxylicacids, and mixtures thereof.

Clause 17. A method according to any one of clauses 13-16, wherein thepolysilazane is present in the liquid polysilazane composition at aconcentration of about 10-50% by weight of the composition.

Clause 18. A method according to any one of clauses 13-16, wherein thepolysilazane is present in the liquid polysilazane composition at aconcentration of about 10-20% by weight of the composition.

Clause 19. A method according to any one of clauses 13-18, wherein theliquid polysilazane is applied to the first side at a thickness thatproduces, upon cure of the polysilazane, a layer of polysilazane havinga thickness of from about 1-10 μm.

Clause 20. A method according to any one of clauses 13-19, wherein theliquid polysilazane is applied to the first side at a rate of about 5-15mL/m².

Having described in detail and by reference to specific examples thereofabove, it will be apparent from the present disclosure thatmodifications and variations are possible without departing from thescope defined in the appended claims. More specifically, although someaspects are identified herein as particularly advantageous, it iscontemplated that the present disclosure is not necessarily limited tothese particular aspects.

What is claimed is:
 1. A laminate comprising a sheet of carbon fiberreinforced polymer (CFRP), the sheet having a first side and a secondside opposite the first side; and a layer of polysilazane covering oneor both of the first side and the second side of the sheet of CFRP.
 2. Alaminate according to claim 1, wherein the first side of the sheet ofCFRP contains perforations.
 3. A laminate according to claim 2, whereinat least one of the first side and the second side of the sheet of CFRPis in electrical communication with a metal.
 4. A laminate according toclaim 2, wherein at least one of the first side and the second side ofthe sheet is in electrical communication with a metal cellular core or ametal alloy cellular core.
 5. A laminate according to claim 4, whereinthe perforations have a diameter of from about 0.75 (0.03 in) to about1.5 mm (0.06 in).
 6. A laminate according to claim 5, wherein thesidewalls of the perforations are coated with polysilazane.
 7. Alaminate according to claim 6, wherein the layer of polysilazane has athickness of from about 1-10 μm.
 8. A laminate according to claim 7,wherein the perforations cover from about 5-20% of the first side of thesheet.
 9. A laminate according to claim 8, wherein the polysilazane isan inorganic polysilazane, an organic polysilazane, or a mixturethereof.
 10. A laminate according to claim 9, wherein the sheet of CFRPcomprises exposed carbon fibers.
 11. A laminate according to claim 10,wherein the metal cellular core comprises aluminum.
 12. A aircraftengine thrust reverser comprising a laminate according to claim
 1. 13. Amethod for inhibiting oxidation of a metal structure electricallyconnected to a sheet of carbon fiber reinforced polymer (CFRP), whereinthe sheet of CFRP has a first side and a second side and the second sideis in electrical communication with the metal structure, the methodcomprising applying a liquid polysilazane composition to at least thefirst side of the sheet of CFRP and allowing the composition to cure.14. A method according to claim 13, wherein the liquid polysilazanecomposition comprises an inorganic polysilazane, an organicpolysilazane, or a mixture thereof.
 15. A method according to claim 13,wherein the liquid polysilazane composition comprises a solution of apolysilazane and a solvent inert to the polysilazane.
 16. A methodaccording to claim 15, wherein the solvent is selected fromhydrocarbons, C₁-C₆ alkyl esters of C₂-C₆ carboxylic acids, and mixturesthereof.
 17. A method according to claim 16, wherein the polysilazane ispresent in the liquid polysilazane composition at a concentration ofabout 10-50% by weight of the composition.
 18. A method according toclaim 16, wherein the polysilazane is present in the liquid polysilazanecomposition at a concentration of about 10-20% by weight of thecomposition.
 19. A method according to claim 17, wherein the liquidpolysilazane is applied to the first side at a thickness that produces,upon cure of the polysilazane, a layer of polysilazane having athickness of from about 1-10 μm.
 20. A method according to claim 19,wherein the liquid polysilazane is applied to the first side at a rateof about 5-15 mL/m².